Sit on the floor and tuck a small medicine ball between your knees. Lie on a mat and touch your hands to the sides of your head. Lift your feet aninch or two off the floor.

Slowly curl your torso up to your midsection while simultaneously raising your knees towards your chest. Hold, slowly return to the starting position and repeat.

Try holding another medicine ball at your chest, elbows out to your sides, while performing the exercise. If you have a partner, have her stand in front of you. As you curl up, throw the ball straight from your chest to your partner. Have her lightly throw the ball back, pull it back to your body, then curl back down.